I think anyone should be able to worship in an SDA Church. If Jesus was OK hanging out with prostitutes so am I. I also have no problem worshiping or hanging out with gays, lesbians transgenders, etc.. No, none of these groups should practice their trade or lifestyles openly at church; and if they do, they should be warned once; and then asked to leave on the second offense. If they are openly gay, promiscuous or otherwise "scandalous, they should not be allowed to hold office - not because they are more "evil" than anyone else; but because their activity is generally considered offensive by most members of church society; and would generally cause a scandal.
That being said, I am sure that there are many discretely gay or promiscuous people serving as pastors, elsders, SS Teachers, Board Members, and Conference administrators. As long as their proclivites are not openly practiced; and the general church population is unaware of them, how are we to even know they are outside of the realm of societal norms? Many sincere believers my have gay, promiscuous and/or transgender leanings (I myself have suffered from heterosexual leanings); but resist them because they believe God when He says "don't do that".
I would not support a church that celebrated gay marriage. I wouldn't condemn them; but I would not support them. It's one thing to accept and love all people where they are; it's a whole other animal to celebrate their sins.